The fractionation of macromolecules by electrophoresis on various supporting media has been carried out in clinical laboratories for a number of years as for screening the blood serum of hospital patients. A cellulose acetate membrane support medium has been recognized as possessing many advantages over filter paper and gels. An apparatus and technique for agar electrophoresis on a plate is described in the article, Nerenberg, S. T. et al., "Laboratory Diagnosis of Specific Organ Diseases By Means of Combined Serum Isoenzyme Patterns," Amer. J. Clin. Pathol. 51:429, 1969. A membrane suspension technique is employed for electrophoresis on cellulose acetate, commonly by means of a so-called "Microzone Cell" sold by Beckman Instruments. It comprises a frame with spring loaded plastic keys which fit into a series of holes punched into opposite borders of the membrane to pull it taut. The membrane portions to the outside of the holes are placed into contact with elongated facing buffer chambers. This elaborate technique was considered necessary to carry out electrophoresis without short circuiting through buffer solution.
The above system has a number of disadvantages. It has been found that approximately half of the relatively expensive cellulose acetate membrane cannot be utilized because of the perforations used for suspension. Also, the lack of rigidity of the suspended membranes renders it difficult to apply a large number of samples at each application. Also different samples requiring different buffers, such as serum and urine, may not be run at one time. In addition, the equipment is relatively expensive and a large amount of technician's time is necessary. Furthermore, the equipment requires the sample to be electrophoresed in the long axis of the membrane which is normally at least three or four times longer than it is wide which results in relatively few samples which can be applied to each membrane. Finally, it is difficult to suspend relatively large fragile sheets of the material to increase the number of samples applied.